Superheterodyne receiver



y 1934; K. POSTHUMUS ET AL 1,968,259

SUPERHETERODYNE RECEIVER Filed Jan. 2, 1952 INVENTORS KLAAS POSTHUMUS WEYERS zWW ATTORNEY Patented July 31, 1934 UNITED STATES rricr' PATENT SUPERHETERODYNE RECEIVER Klaas Posthumus and Theodorus Josephus Weyers, Eindhoven, Netherlands, assignors to Radio Corporation of America, a corporation of Delaware 12 Claims. (Cl. 25020) The present invention relates to superheterodyne receivers, and particularly to that part thereof that follows the intermediate frequency amplifier.

* As is well known, in this stage the acoustic oscillations which in'the end are those desired are modulated on the intermediate frequency oscillationsthe frequency of which is generally of the order of magnitude of from 50 to 100 kilocycles. By reason of this comparatively small large.

number of cycles difiiculties are encountered during detection if in this case a grid condenser is desired to be used, as it is impossible for this condenser to been constructed as to be sufficiently For this reason it is usual to use with this second detector insteadwof a grid condenser an input circuit tuned to the intermediate frequency and consisting of aninductance'and a capacity in parallel. V

According to the present invention, diode detection isused after the intermediate frequency amplifier. In this method also known per se it is necessary to avoid mean frequency potential fluctuations on the control grid of the first low or audio frequency tube. For this purpose use may be made similarly of a series circuit tuned to the said intermediate frequency oscillations, said circuit constituting a short circuit for "the said oscillations. The use of this well known method of detection for the second detector of a superheterodyne receiver has, therefore, in addi-' tion to the knownadvantages generally possessed by this method the advantage that a grid-condenser and the difiiculties incidentalthereto with an intermediate frequency carrier wave are avoided.

Owing to the presence of the said series circuit the intermediate frequency oscillations do not penetrate into the low frequency amplifier. 4. It is,however, found that nevertheless the second harmonic of these oscillations ispresent in it, and may have a harmful effect, particularly, when resistance coupling is used-in the low frequency amplifier. Preferably, therefore, according to 5 the present invention, the lowfrequency amplifier'compri'ses aby-path tuned to the secondhar- 'monic of the-mean or intermediate frequency oscillations Y The novel features which we believe to be char- 9 acteristic of our invention are set forth in particularity in the appended claims, the invention itself, however, as to bothits-organiZation and method of'operation will best'be understood by reference to the following description taken in 5.5 connection with the drawing in which we have input electrodes of the detector and audio ampliindicated diagrammatically several circuit arrangements whereby our invention may be carried into effect. 7

The anode circuit 1 of the last intermediate frequency amplifier tube 20 is coupled to a circuit 2 which is also tuned to the intermediate frequency. The upper end of this circuit is directly connected to the anode 3 of the diode which serves as the second detector, and which is shown combined with the first low or audio frequency tube. Such combination is not essential but assists a concentrated construction'of the device. The other end of the circuit 2 is connected to ground through an inductance 8 in series with a condenser 9 and through a leak! age resistance 22. The path 8,9 is a short circuit forthe intermediate frequency oscillations so that it is only'possible for this end of the circuit 2 tooscillate for low frequency. These low frequency oscillations are supplied through a condenser? to the control grid 4. of a. tube 18, which grid is maintained at. the desired mean-potential by a leakage resistance 10 and a battery 21.

The cathode 5 supplies the electron current both for the diode 3, 5 and for the triode 6; 4', 5. The anode circuit of the tube 18 includes a resistance 11, the anode end of which is connected through a blocking condenser 12 and a series resistance 16 to the control grid of the audiofrequency amplifier tube 17. The grid circuit of this tube includes in parallel with'the usual leakage resistance 13 a tuned series circuit 14, 15 which constitutes a short circuit for the second harmonic of the intermediate frequency. oscillations.

While we have indicated and described several systems for carrying our invention into effect, it will be apparent to one skilled in the art that our invention is by no means limited to the particular organizations shown and described, but 9 that many modifications may be made without departing from the scope of our invention as set forth in the appended claims.

What is claimed is:

1. In a superheterodyne receiver, an intermediate frequency amplifier circuit, a second detector employing diode detection coupled to the circuit, and an audio amplifier coupled to the diode detector and by-pass path, common to the fier, resonant to the intermediate frequency.

2. In a superheterodyne receiver, an intermediate frequency amplifier circuit, asecond detector employing diode detection coupled to'the circuit, and an audiogamplifier coupled to the diode detector, and a by-pass path in the output of the second detector resonant to the second hormonic of the intermediate frequency oscillations.

3. In a superheterodyne receiver, in combination with the intermediate frequency amplifier and an audiofrequency amplifier, a tube including a cathode, a grid, a main anode, and at least one auxiliary anode, an input circuit, resonant to the intermediate frequency, coupled to said first amplifier, said auxiliary anode and cathode being connected to said input circuit toprovide a diode detection circuit, means for coupling the main anode to the input of the said audio frequency amplifier, the said grid being connected to a point on said diode detection circuit whereby said cathode, grid and main anode cooperate to provide an audiofrequency amplifier.

4. In a superheterodyne receiver, in combination with the intermediate frequency amplifier and an audiofrequency amplifier, a tube including a cathode, a grid, a main anode, and at least one auxiliary anode, an input circuit, resonant to the intermediate frequency, coupled to said first amplifier, said auxiliary anode and cathode being connected to said input circuit to provide a diode detection circuit, means for resistively coupling the main anode to the input of said audiofrequency amplifier, the said grid being connected to a point on said diode detection circuit whereby said cathode, grid and main anode cooperate to provide an audiofrequency amplifier.

5. In a superheterodyne receiver, in combination with the intermediate frequency amplifier and an audiofrequency amplifier, a tube including a cathode, a grid, a main anode, and at least one auxiliary anode, an input circuit, resonant to the intermediate frequency, coupled to said first amplifier, said auxiliary anode and cathode being connected to said input circuit to provide a diode detection circuit, means for coupling the main anode to the input of said audiofrequency amplifier, the said grid being connected to a point on said diode detection circuit whereby said cathode, grid and main anode cooperate to provide an audiofrequency amplifier and a by-pass path, series resonant to the intermediate frequency, connected to the said input circuit.

6. In a superheterodyne receiver, in combination with the intermediate frequency amplifier and an audiofrequency amplifier, a tube including a cathode, a grid, a main anode, and at least one auxiliary anode, an input circuit, resonant to the intermediate frequency, coupled to said first amplifier, said auxiliary anode and cathode being connected to said input circuit to provide a diode detection circuit, means for coupling the main anode to the input of said audiofrequency amplifier, the said grid being connected to a point on said diode detection circuit whereby said cathode, grid and main anode cooperate to provide an audiofrequency amplifier and a by-pass path, series resonant to the second harmonic of the intermediate frequency, connected across the input electrodes of the said audiofrequency amplifier.

7. In a superheterodyne receiver, in combination with the intermediate frequency amplifier and an audiofrequency amplifier, a tube including a cathode, a grid, a main anode, and at least one auxiliary anode, an input circuit, resonant to the intermediate frequency, coupled to said first amplifier, said-auxiliary anode and cathode being connected to said input circuit to provide a diode detection circuit, means for resistively coupling the main anode to the input of the said audiofrequency amplifier, the said grid being connected to a point on said diode detection circuit whereby said cathode, grid and main anode cooperate to provide an audiofrequency amplifier and a bypass path, series resonant to the intermediate frequency connected to the said input circuit.

' 8. In a superheterodyne receiver, in combination with the intermediate frequency amplifier and an audiofrequency. amplifier, a tube including a cathode, a grid, a main anode, and at least one auxiliary anode, an input circuit, resonant to the intermediate frequency, coupled to said first amplifier, said auxiliary anode and cathode being connected to said input circuit to provide a diode detection circuit, means for coupling the main anode to the input of said audiofrequency amplifier, the said grid being connected to a point on said diode detection circuit whereby said cathode, grid and main anode cooperate to provide an audiofrequency amplifier, said auxiliary anode being disposed adjacent the cathode outside the electron stream to the grid and main anode.

9. In combination with the intermediate frequency amplifier output circuit of a superheterodyne receiver, a following network comprising a tube including independent diode and triode electrode systems with a common cathode, a circuit, resonant to the intermediate frequency, coupled to said output circuit, the diode electrodes being connected to said resonant circuit to provide a diode detection circuit, a condenser of large capacity connecting the triode input electrode to the detection circuit, and means coupling the triode output electrodes to a load circuit.

10. In combination with the intermediate frequency amplifier output circuit of a superheterodyne receiver, ,a'following network comprising a tube including independent diode and triode electrode systems with a common cathode, a circuit, resonant to the intermediate frequency, coupled to said output circuit, the diode electrodes being connected to said resonant circuit to provide a diode detection circuit, connections, from the triode input electrodes to the detection circuit, and a high resistance for coupling the triode output electrodes to a load circuit, said triode system providing a stage of audiofrequency amplification.

11. In combination, a single tube including independent diode and triode electrode systems with a common cathode, a circuit including a coil and a condenser resonant to an intermediate frequency the diode electrode being connected to the top of said coil, a path of low impedance to intermediate frequency oscillations connecting the bottom of said coil to said common cathode, a condenser arranged to pass audiofrequency currents having one side connected to the bottom of said coil and its other side connected to said triode grid, a load circuit connecting the triode plate with said common cathode, and means for impressing modulated high frequency oscillations on the coil of said resonant circuit.

12. The arrangement defined in the preceding claim in combination with a high leakage resistance having one end connected to said triode grid and its other end to said common cathode.

, KLAAS POSTHUMUS. 1

THEODORUS JOSEPHUS WEYERS. 

